This invention relates to surgical cements derived from calcium sulfate components in combination with certain setting components. More particularly, the present invention relates to surgical cements formed from calcium sulfate components as cementing components and certain soluble salts as setting components. These cements have been found to have controllable setting times and good manipulation characteristics. Potential applications of these cements include use in or as bone cements, dental cements, bone graft materials, bone substitutes, bone fillers, drug delivery systems and binders for granule forms of bioceramic materials.
In the last two decades, many artificial hard tissue implant materials have been made. Among these, bioglass and bioceramics, such as hydroxyapatite and beta-tricalcium phosphate, have excellent biocompatibility. Most of the bioglass and bioceramics for medical applications are prepared either in granule form or block form. The granule form has mobility problems and relatively poor manipulation characteristics, while the block form is quite brittle and difficult to shape. Many attempts have been made to solve the above-noted problems. Among the materials considered have been Plaster of Paris, collagen, different types of calcium phosphate grout or cement, polylactates and polyacrylate cements. None of these materials is completely acceptable.
The surgeon is most interested in implant materials that can be shaped and hardened in situ. Ideally, a useful surgical cement or binder system for hard tissue applications should have the following characteristics: good biocompatibility, a suitable resorption rate, be moldable at the surgical site, and have a controllable setting time with good setting characteristics.
Most developed surgical cements and binder systems have disadvantages. For example, collagenhydroxyapatite and polylactate-hydroxyapatite composites can only be made as premolded shapes and cannot be molded at the surgical site. Plaster of Paris has reasonable setting characteristics but the resorption rate is too fast. Polyacrylate cement is nonresorbable. Polyacrylic acid-calcium phosphate cement is not resorbable and the setting cement is too acidic. Most of the calcium phosphate grouts or cements are prepared by the reaction of calcium phosphate ceramics with an acidic component. See, for example, Bajpai U.S. Pat. No. 4,668,295. In general, these cements are disadvantageously acidic in nature. These calcium phosphate grouts or cements either lack satisfactory mechanical strength or are resorbed too slowly.
It would clearly be advantageous to provide new surgical cements.